1. Field of the Invention
The present invention relates to an image blur correction device correcting an image blur caused by vibration or the like during photographing, a lens barrel having the image blur correction device, and an imaging apparatus such as a digital still camera or video camera having the lens barrel.
2. Description of the Related Art
In recent years, performance of imaging apparatuses such as digital still cameras and video cameras has been remarkably improved, and thus still images and moving images may be easily captured by everyone with high image quality and high performance. Such improvement in performance of imaging apparatuses is largely due to improvement in performance of lenses, imaging devices (such as CCD and CMOS image sensors) and image processing circuits.
However, no matter how much the performance of lenses, imaging devices or the like is improved, a high resolution screen blurs and thus a captured image blurs when hands supporting a camera (imaging apparatus) tremble or shake. Therefore, some relatively expensive cameras have an image blur correction device mounted and correcting an image blur caused by shake or the like during photographing. However, image blur correction may be essentially needed not in high-end models for professional use but rather in popular models used by a majority of the public having only a little photographing experience.
Generally, cameras (imaging apparatuses) are demanded to be reduced in size and weight and are favored to be light and easily carried. However, image blur correction devices of the related art are relatively large. Therefore, when the image blur correction device of the related art is mounted on a camera main body, the camera is large as a whole, contrary to a demand for reduction in size and weight. In addition, an image blur correction device of the related art may need a large number of components and is significantly expensive due to an increase in the number of components, disadvantageously.
Japanese Unexamined Patent Application Publication No. 3-186823 discloses an example of such an image blur correction device of the related art. Japanese Unexamined Patent Application Publication No. 3-186823 discloses a vibration proof device placed in a camera or the like, which detects vibration at a relatively low frequency as information for image blur prevention. The camera vibration proof device disclosed in Japanese Unexamined Patent Application Publication No. 3-186823 (hereinafter referred to as “first related art example”) includes: “a correction optical mechanism placed in a lens barrel holding a lens group to make an optical axis of the lens group eccentric; a vibration detection section detecting vibration applied to the lens barrel; and a vibration proof control section driving the correction optical mechanism based on a signal from the vibration detection section to prevent vibration. The correction optical mechanism includes a correction lens; a fixing frame; a first holding frame; a second holding frame; first and second coils; first and second driving sections; and first and second position detection sections. The fixing frame fixes the correction lens. The first holding frame holds the fixing frame to be movable in a first direction differing from a direction of the optical axis of the lens group. The second holding frame is fixed to the lens barrel and holds the first holding frame to be movable in a second direction differing from the optical axis direction and the first direction, respectively. The first and second coils move the first and second holding frames in the first and second directions, respectively. The first and second driving sections include first and second magnetic field generation members facing the first and second coils, respectively. The first and second position detection sections detect amounts of movement of the fixing frame and the first holding frame in the first and second directions, respectively. At least one of the first and second magnetic field generation members and the first and second position detection sections is provided to a fixed member fixed to the lens barrel and including the second holding frame.”
According to the vibration proof device disclosed in Japanese Unexamined Patent Application Publication No. 3-186823 having such a configuration, it is expected that “the device may respond to high frequency vibration without necessity to increase the cost and ensure a large space (see the section “Effect of the Invention”).
Japanese Unexamined Patent Application Publication No. 3-188430 discloses another example of an image blur correction device of the related art. Japanese Unexamined Patent Application Publication No. 3-188430 discloses a camera image blur suppression device detecting vibration (shake) at a frequency of about 1 Hz to 12 Hz generated in equipment such as a camera as information to suppress an image blur. The camera image blur suppression device disclosed in Japanese Unexamined Patent Application Publication No. 3-188430 (hereinafter referred to as “second related art example”) “determines a correction amount for eccentricity of an optical axis necessary for suppressing an image blur on an image surface based on detected information on vibration generated in a lens barrel and controls movement of a correction optical system floatingly supported to be movable in a diameter direction of the lens barrel according to the correction amount. The floatingly-supported correction optical system includes a first holding frame supporting the correction optical system to be movable in a first direction determined in a plane perpendicular to the optical axis but restraining movement of the correction optical system in other directions; and a second holding frame supporting the first holding frame to be movable in a second direction differing from the first direction in the plane but restraining movement thereof in other directions, the second holding frame fixed to the lens barrel.”
According to the camera image blur suppression device disclosed in Japanese Unexamined Patent Application Publication No. 3-188430 having such a configuration, it is expected that “a problem of defocusing may not occur during suppression of an image blur, and the correction optical mechanism may be formed to have a reduced dimension in an optical axis direction, enabling a camera to be reduced in size.”
However, the first or second related art example includes four guide shafts in total as essential components, specifically, a pair of pitch shafts (guide shafts) slidably supporting a fixing frame having a correction lens; and a pair of yaw shafts (guide shafts) slidably supporting a first holding frame. Therefore, it may be necessary to ensure a space for placing the four shafts, thus increasing an image blur correction device in size, disadvantageously.